LOS ANGELES (AP) — An Al Pacino movie broke out in the middle of a concert by the band Chicago, with thousands of fans serving as extras.

Cameras were wheeled onstage during intermission of the group’s show at the Greek Theatre on Friday night to film a scene from Pacino’s upcoming movie “Imagine,” in which he plays aging rock star Danny Collins.

With coaching from the director, the crowd chanted the name of Pacino’s character as the 73-year-old actor walked on stage to sing “Hey Baby Doll” in a black suit. The movie co-stars Michael Caine, Annette Bening and Jennifer Garner.

“This is an improvisation,” Pacino told the crowd. “You just came in and got it. That’s not easy.”

Chicago’s band members remained on stage to watch and clap along during the 25-minute filming. After a few takes, the crowd grew restless and there was scattered booing for the real musicians to resume playing.

Earlier in Chicago’s set, Joe Mantegna of CBS’ “Criminal Minds” joined his hometown band to sing “If You Leave Me Now.”

Pacino returned to the stage during Chicago’s encore and sang and danced to their hit “25 or 6 to 4.”

“For a shy guy from the South Bronx, this has been great,” Pacino said.